The Hydroponic Cultivation Method for Growing Lettuce

The water contains all the macro and micro-elements consumed by the plant

Elisha Shalgi

September 19, 2017

The greenhouse standing at the outskirts of moshav Kefar Uria looks from the outside like a regular greenhouse of its kind anywhere. But when one steps inside one understands quickly that it is not. The main crop grown in the greenhouse is arabique lettuce.

The lettuce grows on poly-urethane trays and these float on water, in two baths. Namely, this is the hydroponique cultivation method, where the crop's roots do not come in contact with the soil, only with the water in the water baths. The water contains all the macro- and micro-elements consumed by the plant. The water is constantly recycled by two pumps, one for each bath. These pumps are immersed in two water basins at the entrance to the greenhouse. The elements' content is constantly monitored and so is the pH level and the water's oxygen concentration.

The crops in the greenhouse – apart from arabique lettuce, other green crops are grown at a lower scale, e.g., basilicum and mint – are not sprayed against pests. Instead, a very close inspection, by eye and by a magnifying glass, is carried out each day. Also, the entrance to the greenhouse is by two doors. This, in order to eliminate almost completely the entrance of pests from outside .

The air inside the greenhouse is monitored. Namely, the air's temperature and the relative humidity. The air is recycled by two blowers, each of which generates an output of 45,000 cubic meter/hour. These are fixed on the greenhouse walls and when operating, they lower the air temperature by 4-5 degrees. In addition, a system of sprinklers/foggers is installed at the upper part of the greenhouse.

These aid in lowering the air temperature inside the greenhouse. Side curtains make possible, when opened, the entrance of fresh air from outside and when lowered, insure the existence of constant environment conditions inside the greenhouse, e.g., constant relative humidity and air temperature.This, without compromising the well-being of the crops.

A cycle of growth of lettuce lasts usually three weeks. The moment it reaches the proper size it is harvested manually, cleaned, inspected and only then packed inside hermetic plastic bags. The bags are then placed in carton boxes and so are sent to the consumers - be it a consumers' chain, a restaurant or a private consumer. And most important, within a few hours after harvesting.

Phytosanitation is very well kept in the greenhouse. Thus, for example, the used trays are washed by water and detergent after each cycle and then left to dry in the sun. Only after they are dry, are the trays brought back into the greenhouse. This is the story of the hydroponique greenhouse "Kiryat Chasa" close to Kefar Uriya.